Bucket Wheel Excavators: 3D Machine Control on a Large Scale

by Randy Noland, Managing Editor/CoFounder - MachineControlOnline.com

During a recent business trip to Australia, I had the pleasure of visiting several open pit, coal mines. These operations are colossal in scale and because of

their enormity, constant analysis of productivity is extremely important. Even small improvements in their processes yield big dollars. The purpose of this article is to discuss how 3D Machine Control can improve the Bucket Wheel Excavatorʼs safety, accuracy and productivity.

First, a little background. Bucket Wheel Excavators (BWE) are continuous cutting machines for soft to semi hard materials like clay, sand,

gravel, marl and their blending as well as lignite and hard coal. Tenova TAKRAF BWE excavate a wide range of capacities between 200 and 16000 m³/h and at working bench heights from less than 5 m to maximal 51 m.

The BWE is connected to a conveyor belt system. These systems can literally traverse hundreds of meters until they reach their destination; usually a bunker at the power station or spread onto a stockpile awaiting transport.

According to local mine conditions Compact and Large BWEʼs are offered – whereas the selection mostly is determined by required cutting height and width (working block).

The characteristic parts of a BWE are the cutting wheel with buckets, the wheel boom, the superstructure with counterweight boom, the substructure, the undercarriage with

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crawler tracks and a transfer boom to the bench conveyor (or a connecting bridge to the loading unit). All main parts are designed to meet the demands of the project regarding optimization, standardization and maintenance.

BWEʼs are among the largest terrestrial vehicles ever constructed - the biggest machine built, the Tenova TAKRAF SRs 8000, has a weight of 14.200 t and moves 240,000 m³ of overburden per day. <http://www.takraf.com/en/products/miningequipment/bucketwheelexcavator.htm>

Specifically, the RB293 is a giant bucket-wheel excavator made by the German industrial company TAKRAF. It was recorded as the largest and heaviest terrestrial vehicle in the Guinness Book of Records (2001–2009). <http://en.wikipedia.org/wiki/MAN_Takraf_RB293>

HistoryWhile researching the history of Bucket Wheels Excavators, I found this picture shown to the right. This is one of two bucketwheel excavators fabricated in the Lauchhammer works, in 1926.

In 1990, TAKRAF Schwermaschinenbau AG manufactured their 500th bucketwheel excavator and in 2005, production reached completion for the 1000th.<http://www.takraf.com/en/aboutus/history/main.htm>

I was in awe at the sheer size of these machines but had no idea of their long history prior to preparing this article.

New Technology Meets Traditional Brawn New life has been given to this massive historical workhorse. The Bucketwheel Excavator is an excellent candidate for 3D Machine Control. One of the sites I visited had 5 Bucketwheels retrofitted with 3D Machine Control. It was amazing to see 5 of these 6+ story tall machines munching away, almost silently, at the coal.

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Letʼs discuss briefly the general anatomy of a 3D Machine Control Bucketwheel. First, there is a dual GNSS receiver installed. One GNSS antennae is installed at the center or pivot point. This offers a base position for the machine and proximity to the site and surface. The second GNSS antennae is positioned so as to monitor the arm swing. Both GNSS positions also provide heading. There are also a series of axial sensors installed at strategic locations to monitor all articulation. (See picture)

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System Component Placement

The Operators CabThe operatorʼs cab is as big as small apartment I once rented in the San Francisco Bay area. The cockpit rivals a commercial jet. All of the sensors feed into a computer system loaded 3D Machine Control Software. The software calculates (in real time) all

positioning information presenting the operator with simple to follow instructions for cut/fill, productivity and machine proximity on the site. A radio system

wirelessly transmits this data in real time back to the mining office for each of the 5 machines. A command and control center receives this data in real-time while logging to a database for further analysis. Reports and playback are also possible. The office software can also send data to all BWEʼs over the same wireless network.

BenefitsSeveral benefits are realized by retrofitting the BWE with 3D Machine Control. First and foremost is safety. No longer does a person need to be at the cutting wheel measuring surface progress nor does the machine have to stop to accommodate this task. The accuracy is greatly improved at +/- 50 mm. And productivity gains increased due longer time periods of uninterrupted operation while calculating the volume of coal, real-time. This is key for producing the right amount of coal based on the power plants fluctuating demands

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Current Accuracy at bucket teeth

Software User Interface

Yours truly at the controls

SummaryThere is a responsibility for providing the best energy at the best price. The mining industry is ever challenged in this quest. By implementing new and emerging technologies, the industry has proved that advances can be realized without losing the investments of past implementations. RN July 2009

Video NoteI will be posting a video presentation of footage I gathered while on site. Please check the front page of MachineControlOnline.com and our Exclusive Video section.

MachineControlOnline.com July 2009